What are the heating methods for low-temperature batteries?

The external heating method of lithium battery is one of the most widely used heating methods. The battery is heated by an external heat source. Its important feature is its simple structure. However, the external heating efficiency is very low, so it consumes a lot of power. At the same time, it is easy to cause inconsistent internal temperature gradients of the battery, leading to inconsistent internal failures of the battery and affecting the service life of the lithium battery. Liquid has a higher thermal conductivity and capacity than air, so the heat transfer efficiency is higher, but in contrast, the liquid preheating system is more complicated. According to whether the battery is in contact with hot liquid during the heating process, liquid heating can be divided into two categories: 1) non-contact heating; 2) immersion heating. Typical liquid preheating system structure. Currently, non-contact liquid preheating systems have been applied to electric vehicles. For example, Volt uses a 360V heater to heat the liquid and then transfer it to the battery. The air preheating air temperature control system has been widely used in the field of electric vehicles due to its simple structure and low cost. The basic working principle of the air conditioning temperature control system is to heat the outside air through the heating system, and then enter the battery pack to heat the battery under the use of a fan. Air preheating is generally used, and the heating speed can reach 0.5-3°C/min. The air flow speed and temperature affect the air preheating effect. Relevant research shows that increasing the air velocity is more obvious than increasing the air temperature. At the same time, the increase in air temperature will also make the internal temperature gradient of the battery more obvious, which will adversely affect the battery life. Honda Insight and Toyota Prius have used this technology, but it still has many shortcomings, such as noise and efficiency. Phase change material preheating, air preheating and liquid preheating require more complicated battery internal structures, such as pipes, pumps, heaters, etc., which increase the cost and design difficulty of battery packs. It provides a relatively simple method for battery pack preheating and phase change materials. This method is important to achieve the purpose of battery heating and cooling through the heat release or absorption of phase change materials during the phase change process. The thermal conductivity of the material is generally low, which is not conducive to the rapid heat transfer of the battery. In order to solve this problem, people have proposed a method of connecting the carbon nanotube framework to the metal, but the current method is still in the laboratory stage and has not yet been applied. Electric heater preheating In addition to the above preheating methods, we can also preheat the battery through electric heaters. Electric heaters are divided into: 1) Peltier effect heater; 2) Peltier effect heater. 2) Electric heating plate; 3) Electric heating cover; 4) Electric film. The multiplier effect heater heater forms a hot surface and a cold surface on both surfaces by the Pettil effect of the semiconductor. By controlling the direction of the current, the position of the hot and cold sides can be controlled to achieve the purpose of cooling or heating the battery. The temperature can be controlled by controlling the amplitude of the current. In this way, a heating rate of 0.6-1°C/min can be achieved, and the energy consumed by the preheating battery accounts for about 2.5% of the total battery energy. Heater preheating In the heating mode of electric heating plate, the electric heating plate is generally placed on the top or bottom of the battery, and the heat generated by the electric heating plate is directly transferred to the battery. Electric heaters are generally made of positive temperature coefficient material (PTC). As the temperature increases, the resistance increases, so as to achieve the purpose of automatic temperature control. Disclaimer: The articles published on this website are all from the Internet. If there is any infringement, please contact to delete it. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: The correct use and service life of lithium batteries